community/py3-django: security upgrade to 4.2.10

Includes:

• https://docs.djangoproject.com/en/5.0/releases/4.2.8/
• https://docs.djangoproject.com/en/5.0/releases/4.2.9/
• https://docs.djangoproject.com/en/5.0/releases/4.2.10/ (CVE-2024-24680)

Also remove an old Python 3 symlink.